📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/call-bound/index.js

@@ -0,0 +1,19 @@
+'use strict';
+
+var GetIntrinsic = require('get-intrinsic');
+
+var callBindBasic = require('call-bind-apply-helpers');
+
+/** @type {(thisArg: string, searchString: string, position?: number) => number} */
+var $indexOf = callBindBasic([GetIntrinsic('%String.prototype.indexOf%')]);
+
+/** @type {import('.')} */
+module.exports = function callBoundIntrinsic(name, allowMissing) {
+	/* eslint no-extra-parens: 0 */
+
+	var intrinsic = /** @type {(this: unknown, ...args: unknown[]) => unknown} */ (GetIntrinsic(name, !!allowMissing));
+	if (typeof intrinsic === 'function' && $indexOf(name, '.prototype.') > -1) {
+		return callBindBasic(/** @type {const} */ ([intrinsic]));
+	}
+	return intrinsic;
+};